davidgooding

Have you asked on the Large Format Photography Forum?

No I haven't actually - I'll head over there and ask. Thanks!

Did you check to see if that metering frame and probe are covered by patents from Sinar or Gossen?

Thanks for your input. I did do a patent search and I am not infringing any patents that I know of. However I'll run some more specific searches for Sinar and Gossen.

This unit does not have a special metering back for the camera (unlike the Sinar meter) but instead is a relatively cheap and cheerful thing using a frame that inserts in place of the film carrier with dimensions compatible with a standard film carrier. This frame accommodates a moveable metering probe through a slot in the top. The price you pay for this is a slight defocussing of the image while you are metering due to the rearward movement of the ground glass when the frame is inserted, approx 9mm.

Hi All,

It's been quite a few years since I was last on here.

I'm not actually a photographer! I don't have the artistic skill necessary for that and am an engineer by trade and nature instead.

A few years ago I made a post here about whether a low-cost focal-plane metering system for large format cameras would be a useful product, after having developed one for my father (he has a Sinar P), and I got quite a bit of positive response and helpful suggestions.

After that, life got in the way and I did nothing much further with it. However, more recently, after having refined the design and providing a few more for large format photography hobbyists (and developing it further each time with their input), I have decided to take this further. I have therefore put in some effort over the past year to productionise the design, have produced a production batch, and am now taking steps towards marketing it.

Basically it consists of a metering frame, which is inserted in place of the film carrier, which contains a metering probe which can be moved around the image to meter at specific points in the image. There's a picture below to give the general idea.

At the time I originally started this, there were other meters of a similar concept on the market but at prices that were out of reach of many. The aim here was to produce a more basic, but still accurate, useful and reliable, meter at a much more affordable price.

Do people consider that this is a useful product, and one which people would seriously consider at the price point I can achieve (£120, or roughly US$160, or Euro 140)?

Are there any suggestions, questions or comments on the design?

Do significant numbers of people still use film anyway?

I have put it up on the internet here if anyone is interested in taking a closer look - www.dlgelectronics.com. I'll go further with this if people think it worthwhile.

I would also be interested in developing further products if (1) this proves at least moderately successful and/or (2) anybody has any ideas or requirements for similar things.

Thanks for your interest!

Dave

Thanks All - I was really pleased to see all the encouraging responses. I think that I'll proceed and get a small batch manufactured.

I think, having read through other correspondence on this site, that this is not called a spot meter - I don't know what you call it but the metering probe is inserted into the back of the camera in front of (i.e. the lens side of) the ground glass and is positioned wherever a reading is desired - my father uses it for example to ensure that detail in shadows is within the EV range of the film. He photographs mainly architectural subjects.

Paul, I can email some photos of the prototype (+ draft instruction manual) if you like or I could try putting the photos in the Gallery if I can figure it out. I've put a photo in this response - it doesn't show the meter scale as that is on the top panel. I apologise for the quality of the photograph - with a gloss black finish it didn't come out well and I'm not a photographer. I'll ask my father to produce some better pictures. Note that the production version is likely to differ somewhat in the finish (better, I hope!) and that the metering probe pictured is just a gash one - the production version would be of different design as the perspex affects the readings by leaking light into the camera.

Roger ﾖ thanks for the offer of a review ﾖ if I go ahead Iﾒll be in touch. I expect it will be month or two from now as I want my father to complete his trials and calibration first. I shall try to keep the cost down to around 100 pounds each (I think thatﾒs around $175).

Thanks again to all.

Dave.<div></div>

Hi,

I made a spot meter for my father who uses a 4x5 Sinar, as he couldn't justify

the high cost of buying one. (I'm an electronics person rather than a

photographer). He has suggested that the unit may be of interest to others as

being a basic and relatively low cost item, yet of high-quality construction

and of professional appearance. I'm therefore asking if people feel that it

would be useful producing a few.

What I made comprised a metering probe approx. 11 inches long containing a

sensor approx. 1/4 inch across, which connects via a cable and jack plug into

a box approx. 4.5 by 6 inches 1 inch deep containing controls and analogue

display. You set the exposure value and film speed on the controls and the

display indicates the relative brightness/darkness referenced to some notional

mid-grey on a scale of +/- 4 stops - you then adjust your exposure as

necessary to acheive the desired range.

The usable exposure range is from 1/2000s to about 4 hours or so at 125 ASA.

The accuracy and linearity was good enough to reveal small errors in the f-

stop settings of his lens. There's also two memories, where you can hold the

brightness value of particular parts of the image whilst looking at another.

The whole thing weighs about 12 ounces and runs off a PP3 battery (approx 50

hours running time). It would cost me approx ﾣ100 to ﾣ130 to produce depending

on quantity and I wonder if people think that this would be worth doing?